HELP with GM 350 timing

[Dimitri]

Hello,

I have a 32' Thompson with what an engine that says GM 5.0L B on the block. I asked around and was told that it's a GM 350 engine. I am trying to figure out what is the proper timing on that engine. I just set it to "8 before", it's working alot quiter, but I can't get the RPM to go up above 2700 at full throttle with stern drive in gear. Before I could get it to 3200. And I am being told that the normal operating RPM for that engine should be 4000-4500. I have Aquanatics 290 Stern drive with 15/19 single props. The boat is dual engine/single prop, by the way. Also, the intakes were replaced with Edelbrock performance intake and it has 600 Edelbrock carbs. Any help on the subject would be greatly appreciated!!! Many thanks ahead of time.

Dimitri

[gonzo]

It is a 305 engine. What kind of ignition system do you have? The base timing setting procedure varies with models.

[BJB]

Gonzo is right - they are 305's. Same block as 350 but different bore & stroke. You may also be overpropped for those outdrives. I have a single 280 outdrive on a 28' Bayliner (AQ260 - 5.7 GM) and had to reduce pitch significantly to stop over-loading the engines (WOT only doing 3800). You might want to call your local Volvo dealer.

[messabout]

Small block Chevy engines have a range of ignition timing from about 34 degrees to as much as 40 degree. Use the timing light to determine what you have. The timing figures are to be applied to the engine when it is turning fast enough to have allowed the distributor to go to full advance condition. that'll be in the 2500 to 3000 RPM range.

Set the timing at the lowest advance that the engine is happy with. Ignition timing is determined by the type of heads, the compression ratio, and the type of fuel you are using.

Your posting uses the plural "carbs". Are we to presume that you have dual 600s. If so, you are almost surely overcarbureted. The manifold has some, but not a lot of bearing on the ignition timing. Edelbrock makes a whole mess of manifolds. With the changes you have made to the engine, there is a distinct possibility that you have condition that is called "wet flow". The air fuel mixture that enters the manifold, then to the ports and then across the valve heads, make a circuitous path. The fuel is centrifuged out of the air/fuel mixture as it turns all those corners. Then the fuel runs into the cylinder in little rivulets. Wet fuel does not burn well or rapidly. In such cases the ignition timing must be advanced more than normal. These are things that the good folks at Edelbrock and Weiand and others do not tell you. This is not to indict them or accuse them of chicanery. Their products work well in the hands of knowledgable tuners but can cause more problems than they solve for casual mechanics.

I work on race engines almost every day. A small block Chevy or Ford is very capable of making 500 HP on a single 4 barrel carburetor and well over 400HP on a two barrel. No way in hell you need two carbs on one engine. Furnishing fuel to the engine is not the problem. Furnishing air is the real problem. You need about 14 pounds or air to burn one pound of fuel. Observe the word pounds. The 14 to one ratio is called stoichiometric ratio. that is the ratio that has an oxygen content sufficient to burn all the fuel that the air/fuel mixture contains. It takes a huge volume of air to make a pound. So hot rodding the engine is a matter of getting a sufficient volume of oxygen bearing air to the combustion chamber and not a matter of delivering more fuel.

Sorry about the soap box sermon. I hope some of it might be helpful.

[ianper]

I have a problem with my volvo (ford 351 carb) engine with sx drive on a campion 245. It starts ok, revs high, Only problem is that when the engine warms up and i slow down to idle speed, the engine dies. After that its impossible to start. It takes about half an hour or so. Another problem is that the distributor is jamed. Think the previous owner sealed (glued) it onto the engine so i can't adjust the timing. Any help would be good.

[alan white]

Ianper, It's not your timing, I think. Sounds like a fuel problem, probably a simple carburator adjustment. Otherwise, look for vapor lock. See if this happens more in hot weather, or if your fuel line is being heated by the engine prior to the fuel pump. If so, relocate the fuel line to a cooler place.

More than likely, the distributor is just stuck. If you can get a forked wedge of wood underneath it and rap that a few times gently, it should come out.

Dimitri, you can adjust the distributor underway, which will show whether timing is the problem. Advancing slowly until engine knocks, then back off a little. Not exact, but very effective.

Alan